The invention relates to gene mutations that predispose an individual to cardiac disease, obesity, and diabetes. More specifically, the present invention relates to specific polymorphisms in the xcex21- and the xcex22-adrenergic receptor genes. The invention further relates to methods and molecules for identifying one or more polymorphisms in the xcex21- or the xcex22-adrenergic receptor genes.
Beta adrenergic receptors (xcex2AR) are the receptors for the endogenous catecholamines, epinephrine (adrenaline) and norepinephrine (noradrenaline). There are at least nine sub-types of adrenergic receptors (H. G. Dohlman et al., Annu. Rev. Biochem. 60:653-688 (1991); S. B. Liggett et al., In: Catecholamines, Bouloux, ed. W. B. Sounders, London (1993)), of which at least three sub-types are xcex2-adrenergic receptors.
The xcex21- and xcex22-adrenergic receptors (xcex21AR, xcex22AR) are expressed in many organs in the body, including heart, lung, vascular tissue, and pancreas (S. B. Ligget In: The Lung: Scientific Foundations, R. G. Crystal et al. (ed.) Lippincott-Raven Publishers, Philadelphia (1996); J. R. Carstairs et al., Am. Rev. Respir. Dis. 132:541-547 (1985); Q. A. Hamid et al., Eur. J. Pharmacol. 206:133-138 (1991)). In the heart, one or both of these receptors regulate heart rate and pumping function; in the lung the xcex2AR regulate airway tone; in the vasculature they regulate vascular tone; in adipose tissue they regulate lipolysis; and in the pancreas they contribute to insulin release. These receptors mediate not only the actions of adrenaline and noradrenaline, but a host of synthetic agonists as well.
The xcex21 adrenergic receptor has been cloned and sequenced (T. Frielle et al., Proc. Natl. Acad. Sci. (USA) 84:7920-7924 (1987)). The gene has been localized to chromosome q24-q26 of chromosome 10 (T. L. Yang-Feng et al., Proc. Natl. Acad. Sci. (USA) 87:1516-1520 (1990). The human xcex21AR has a deduced amino acid sequence of 477 amino acids and is structurally similar to the xcex22AR in many respects. Only a single polymorphism (identified by restriction fragment length polymorphism analysis (RFLP)) has been reported in the human xcex21AR (W. H. Berrettini, et al., Nucl. Acids Res. 16:7754 (1988). To date, polymorphisms resulting in amino acid changes in the xcex21AR protein have not been reported.
The gene encoding the human xcex22AR has also been cloned and sequenced (B. K. Kobilka et al., Proc. Natl. Acad. Sci. (USA) 84:46-50 (1987)). It is an intronless gene that has been localized to q31-q32 of chromosome 5. The deduced amino acid sequence consists of 413 amino acids, with seven clusters of hydrophobic residues thought to represent transmembrane spanning domains. The N-terminus is extracellular, containing two sites for asparagine-linked glycosylation. The transmembrane spanning domains are connected by three extracellular and three intracellular loops. The C-terminus is intracellular. Several polymorphisms in the xcex22AR gene sequence have been reported (E. Reihsaus et al., Am. J. Resp. Cell. Mol. Biol. 8:334-339 (1993); K.-U. Lentes et al., Nucleic Acids Res. 16:2359 (1988); and C. K. McQuitty et al., Hum. Genet. 93:225 (1994)).
Polymorphisms in the xcex22AR have been studied in the context of asthma (E. Reihsaus et al., Am. J. Resp. Cell. Mol. Biol. 8:334-339 (1993), herein incorporated by reference; K. J. Holroyd et al., Am. J. Respir. Crit. Care Med. (Abstract) 151:A673 (1995); D. M. Cooper et al., Am. J. Respir. Crit. Care Med. (Abstract) 153:A254 (1996); K. S. Tan et al., Am. J. Respir. Crit. Care Med. (Abstract) 155:A208 (1997)). There appears to be no difference in the distribution of xcex22AR polymorphisms between individuals suffering from asthma and normal individuals. There is evidence, however, of an association between one polymorphism and more severe asthma (Reihsaus et al.). More recently, these polymorphisms have been shown to be associated with the nocturnal asthmatic phenotype (J. Turki et al., J. Clin. Invest. 95:1635-1641 (1995)), bronchial hyper-reactivity (I. P. Hall et al., The Lancet 345:1213-1214 (1995)), and IgE levels (J. C. Dewar et al., J. Allergy Clin. Imm. (In Press)). Using site directed mutagenesis and recombinant expression in fibroblasts, the pharmacologic properties of these variants have been assessed in vitro (S. A. Green et al., J. Biol. Chem. 268:23116-23121 (1993); S. A. Green et al., Biochemistry 33:9414-9419 (1994))and in transgenic mice (J. Turki et al., Proc. Natl. Acad. Sci. (USA) 93:10483-10488 (1996)).
Given the importance of the xcex21- and the xcex22-adrenergic receptors in modulating a variety of physiological functions, there is a need in the art for improved methods to identify these polymorphisms and to correlate the identity of these polymorphisms with the other functions of xcex2-adrenergic receptors. The present invention addresses these needs and more by providing polymorphisms, molecules, and methods useful for the diagnosis and prognosis of cardiovascular diseases, obesity, and diabetes.